1. Field of the Invention
The present invention relates to a gas burner, and more particularly, to a swirler plate in a gas burner in which gas is burnt.
2. Background of the Related Art
In general, the gas burner is an appliance for burning a gas (LNG, LPG, and the like) for room heating and etc., using a heat from the combustion. A related art gas burner will be explained with reference to FIGS. 1 and 2.
There are a suction grill 2 in a lower portion of a body 1 for drawing external air, a discharge grill 3 for discharging heated air having a heat exchanged in the gas burner in an upper portion, a combustion chamber 4 in the body 1 for burning gas, a fan housing 5 for placing a fan 5a under the combustion chamber, and a heat exchanger 7 above the combustion chamber. And, there is a gas discharge pipe 8 connected to the heat exchanger for discharging exhaust gas to outside of the room an air supply pipe 9 connected to the combustion chamber, and a fan 9a at an outlet of the air supply pipe 9 for drawing air.
In the meantime, there is a burner unit in the combustion chamber 4 for mixing air and gas, and igniting the mixed gas, to make a flame, to which a gas supply pipe 6 is connected. The burner unit will be explained in detail with reference to FIGS. 3.about.5.
There is a draft tube 20 provided with a nozzle 10 having a plurality of gas spray holes 11 at an end thereof for mixing gas and air and supplying the mixed gas to the combustion chamber, a flame detector 30 and an ignition plug 40, one end of each of which is passed through the draft tube and projected into the combustion chamber. The draft tube 20 has a tube body 21 and a swirler plate 22 formed as a unit in front of the tube body. The swirler plate 22 has a plurality of slits 23 formed in a radial direction for supplying the mixed gas to the combustion chamber, and swirl vanes 24 on one side of the slits 23 for guiding the mixed gas toward the combustion chamber. The swirl vanes 24 are oriented in one direction and have the same slopes, for providing the mixed gas discharged through the slits with a circulating force to make a smooth mix of the gas and the air, and a strong injection force to the mixed gas. Accordingly, external air and gas are mixed in the draft tube 20, and injected into the combustion chamber 4 through the slits 23 in the swirler plate 22. The gas sprayed through the gas spray holes 11 in the nozzle can be directed to the slits 23 smoothly because the orientation of the slits 23 in the swirler plate is within a spray span of the gas sprayed through the gas spray holes 11 in the nozzle. That is, since an end of the nozzle 10 having the gas spray holes formed therein is sloped an angle, such that a direction of the gas spray hole 11 corresponds to a direction of the slits 23. The ignition plug 40 ignites the mixed gas sprayed into the combustion chamber, the flame detector 30 determines an occurrence of a flame, which is in general of an AC flame detection type using an FET (Field Effect Transistor). That is, ignition, i.e., occurrence of the flame is detected by the flame detector 30 and the ignition plug 40 is controlled according to a result of detection.
The operation of the gas burner will be explained.
Upon putting the gas burner into operation, a controller(not shown) controls an air supply fan 9a to rotate, to draw external air and gas. The drawn air and gas are mixed appropriately and sprayed into the combustion chamber 4 through the slits 23. The mixed gas sprayed into the combustion chamber is ignited by the ignition plug 40 to form flame in the combustion chamber 4. The flame detector 30 detects the flame ignited initially and inputs to the controller, so that the controller compares a value of the flame detection to a present flame reference value. If it is determined that the mixed gas is ignited normally as a result of the comparison, operation of the ignition plug 40 is stopped so that no more flame is formed. That is, the flame detector 30 measures a flame voltage of the mixed gas, to determine formation of the flame and a state of the flame during operation.
In the meantime as shown in FIG. 4, the flame at the swirl vane diverges, to form a combustion main reaction region `B`(a region the flame voltage caused by flame ions is the highest) at outer periphery, and there is almost no flame voltage in other regions. However, the flame detector 30 can be positioned, not in the combustion main reaction region of the slit(called as "a first slit". Defined as "flame detector swirl vane") 23b, but in combustion main reaction region of a slit (called as a second slit)23b right before the first slit 23a. Accordingly, the flame detector detects formation of a flame discharged through the second slit.
A structure of the burner unit for the related art gas burner has the following problems.
First, accurate detection fo flame formation and a flame state have been difficult in the related art. Because, as explained, the flame detector detects a flame, not at the first slit, but at the second slit. However, the flame discharged through the second slit is directed upward by a second swirl vane slope, such that the flame detector can detect only a portion of the flame form a region of an intensive flame, to fail an accurate detection of formation of the flame (see FIG. 6). Due to this, in order to solve this problem in the related art, a shape of the flame detector is modified, or an overall height of the flame detector is made higher, However, the above measure pushes up a cost since the flame detector is expensive, and has problems in view of fabrication, i.e., fastening of the flame detector and swirler plate, formation the flame detector. The elevation of the overall height of the flame detector rather causes malfunction for influences of external environment, such as noise signal, deformation coming from a prolonged use, and interference with other components.
Second, though the gas burner is required to maintain a flame constant during operation, the related art gas burner has occasions in which the flame is either unstable or out due to a momentary drop of a gas pressure. Because a momentary flow of much air through the air supply pipe causes a momentary low pressure of the supplied gas, with a sharp reduction of discharge fuel, that increases a fuel to air ratio, to result in an unstable flame or flame out.
Third, the poor ignition performance of the related art gas burner has occasions in which ignition is delayed or failed due to poor ignition. Because the related art swirl vanes 24b of a planar form sprays the mixed gas evenly throughout the slit 23b, that causes discharged ignition nuclei not to concentration on an end of the ignition plug, but dispersed(see FIG. 5).